球状、立方状及空心立方状PbS纳米晶的控制合成及其形成机理

以醋酸铅为铅源,硫代乙酰胺为硫源,在表面活性剂十二烷基硫酸钠(SDS)和十六烷基三甲基溴化铵(CTAB)共同作用下,通过简单地调节水热反应的反应温度控制合成出球状、立方状和空心立方状PbS纳米晶。利用XRD、TEM对合成产物的结构和形貌进行了表征,发现合成的球状、立方状和空心立方状PbS纳米晶尺寸均一,直径为100 nm左右。对球状、立方状和空心立方状PbS纳米晶的形成机理进行了初探,结果表明反应温度较低时,水热反应初始阶段形成的PbS小颗粒呈球形,在表面活性剂SDS的烷基链模板和CTAB微胶束软模板共同作用下生成球状PbS纳米晶;反应温度较高时,水热反应初始阶段形成的PbS小颗粒由于自身的立方相岩盐晶体结构的影响有呈立方状趋势,在SDS和CTAB共同作用下产物堆积成空心立方体状或立方状。     

液相合成方形PbS纳米晶的光学特性

采用一种简单、温和的液相合成方法制备了PbS纳米晶，利用透射电镜和高分辨透射电镜对PbS纳米晶的形貌与晶型结构进行了表征．研究了PbS纳米晶的光学吸收和光致发光特性，并比较分析了包覆剂聚乙烯吡咯烷酮(PVP)和回流时间对产物光学特性的影响．结果表明：PVP分子链中的O原子与纳米晶表面吸附的游离态Pb原子形成Pb-O配位键，使产物的激子吸收大为减弱，同时引起了表面浅束缚态能量的升高，最终导致了荧光淬灭现象．     

PbS纳米微粒对溴化银微晶乳剂的化学增感作用

发现了PbS纳米微粒对溴化银乳剂的化学增感作用,对PbS和Na₂S₂O₃对卤化银乳剂的增感作用进行了比较,研究了增感剂用量、增感温度和pAg值、溴化银的晶型等因素的影响,以及PbS纳米微粒与HAuCl₄的协同增感效应.     

简捷溶剂热技术制备纳米棒基PbS树枝晶

以氯化铅和硫氰酸钾为原料,乙二醇为溶剂,采用简捷溶剂热技术制备了半导体PbS纳米棒基树枝晶。粉体用XRD、XPS、FESEM、TEM和ED进行了表征。单个PbS树枝晶具有三维空间结构,由一个主干和四个相互垂直侧枝组成。主干长2～10 μm,直径150～300 μm,每组侧枝纳米棒相互平行,沿主干垂直生长,棒长0.1～1.5 μm,直径80～180 nm。并对生长过程进行了探讨。     

生物大分子控制的硫化铅纳米结构材料的合成

本文在常温,常压,自然pH条件下,利用常温沉淀方法,以生物大分子为模板,矿化合成了硫化物新型形貌纳米结构材料。以硝酸铅(Pb(NO3)2)和硫代乙酰胺(TAA)为原料,进行了矿化实验,实验结果采用扫描电镜(FESEM)、表面能量色谱分析(EDS)、X射线衍射(XRD)、红外光谱(FTIR)等表征分析,结果表明,以鱼精DNA为模板,得到了长棒、短棒、花状结构的PbS纳米结构;以牛血清白蛋白(BSA)为模板,得到了纳米立方体PbS纳米结构,制得的PbS微纳米晶属于面心立方晶系。     

立方体形PbS纳米晶的制备

在60～100 ℃下，以醋酸铅为铅源，硫代乙酰胺为硫源，乙二胺为溶剂，制备了立方体形的PbS纳米晶，采用XRD、TEM、SAED、SEM等对合成的产物进行了形貌和结构的表征。结果表明得到的产物为单晶的立方体形PbS，颗粒大小均匀。并且随着反应时间的延长，反应温度的升高，硫源比例的增加，立方体变大。通过控制不同的反应条件，可以合成边长从几十个纳米到几百个纳米的立方体形PbS晶体。     

W/O型微乳液中不同形貌PbS纳米粒子的制备及其形成机理的探讨

用聚乙二醇辛基苯基醚(OP)/异辛醇/环己烷/水溶液所形成的微乳液体系控制合成出了PbS纳米粒子，考察了微乳液中水与表面活性剂的物质的量的比(ω₀)、反应物浓度及浓度比、陈化时间等条件对产物形貌的影响。采用透射电子显微镜(TEM)、X-射线衍射(XRD)分别对产物的结构、粒度和形貌进行了表征。结果表明，在微乳液体系中，控制不同的实验条件，可以成功地合成球形、梭形、针状和棒状的PbS纳米粒子，并且粒径分布集中，无团聚现象。论文还对不同形貌PbS纳米粒子的形成机理进行了探讨。     

不同形貌PbS 纳米粒子形成机理的探讨

采用聚乙二醇辛基苯基醚(OP)/正戊醇/环己烷/水溶液所形成的W/O型微乳液中的水核作软模板,合成了不同形貌如球形、立方体形、纺锤形、梭形和棒形的PbS纳米粒子。运用透射电子显微镜(TEM)对产物的形貌进行了表征。考察了W/O型微乳液中水与表面活性剂的物质的量的比(ω0)、反应物浓度和陈化时间等条件对产物形貌的影响。对不同形貌PbS纳米粒子的形成机理进行了探讨。     

花生酸单分子膜诱导PbS晶体取向生长的研究

以花生酸单分子膜为模板，诱导沉积了PbS半导体纳米粒子，粒径为30～50 nm.实验发现， 由于花生酸单分子膜的诱导作用， 使得PbS晶体在膜上发生取向生长，可以形成三角形、四边形和棒状的PbS纳米粒子.通过改变单分子膜的表面压，考察了表面压对PbS晶体取向生长的影响，结合透射电镜及电子衍射实验，对PbS晶体的生长机制进行了初步的分析和探讨.     

PbS/RL~2(NCS)~2复合敏化SnO~2纳米多孔膜电极的光电化学研究

用光电化学方法和UV-vis吸收光谱研究了PbS和Rul~2(NCS)~2(L=2,2'--bipydine--4,4'-dicarboxylicacid)复合敏化SnO~2纳米晶多孔膜电极的光电化学行为.实验表明,复合敏化比用PbS或RuL~2(NCS)~2分别单独敏化的效果好,不仅使电极的光吸收拓展到可见光区,而且复合敏化显著提高了光电转换效率,并讨论了复合敏化电极的电荷传输机理。     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

Microwave-assisted copper-catalyzed stereoselective ring expansion of three-membered heterocycles with α-diazo-β-dicarbonyl compounds

Microwave-assisted copper-catalyzed ring expansions of three-membered heterocycles with α-diazo-β-dicarbonyl compounds were investigated. Thiiranes generated 3-acyl-5,6-dihydro-1,4-oxathiines in the presence of copper sulfate and trans-3-acyl-5,6-dihydro-1,4-oxathiines as stereospecific products for 1,2-disubstituted cis-thiiranes through an intramolecular S_N2 process. Oxiranes gave rise to 2-acyl-5,6-dihydro-1,4-dioxines under the catalysis of copper hexafluoroacetylacetonate and cis-3-acyl-5,6-dihydro-1,4-dioxines as stereospecific products for 1,2-disubstituted cis-oxiranes via an intimate ion-pair mechanism. The current method provides a direct and simple strategy in efficient preparation of 3-acyl-5,6-dihydro-1,4-oxathiines and 2-acyl-5,6-dihydro-1,4-dioxines, important agents in medicinal and agricultural chemistry, from readily available thiiranes and oxiranes, respectively.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.